2O2 LOUISE H. GREGORY. 



(b~) Direct Response of Older Protoplasm to Beef Extract. 



Table II. shows the results of feeding Uroleptus with the beef- 

 flour medium when the protoplasm was older than in the experi- 

 ments shown in Table I. Series 97, 98.8, 99$, iooB, lOiB, all of 

 which had been depressed in the beef-flour medium when tested 

 earlier in their life history, now are stimulated by the treatment. 

 Series 97 during the 6o~75th generations showed an increase in 

 ten days of 6.8 divisions per line over the control series. The 

 stimulating effect of the beef was seen again though to a less 

 degree in the i67th generation and even in as late a period as the 

 225th generation, the beef series maintained a slightly higher 

 rate of division than the control. Series 98.8 depressed in the 

 4Oth generation, was stimulated in the 75th and I22d generations 

 and at both times, the division rate exceeded that of the control. 

 This same increase it vitality was observed in varying degrees in 

 Series 99-B, lOoB, and 101.8 each one having been previously 

 depressed by the beef treatment. In addition to the above 

 experiments, three other series were tested whose reaction to beef 

 in their earlier history was not known. Series 72 was in its 5Oth 

 generation when it was obtained from Columbia. A series was 

 treated with beef for 40 consecutive days and throughout the 

 entire period from the 5Oth to the i4Oth generation, the stimu- 

 lating effects of the beef were apparent. Even in the iSoth 

 generation the division rate of the beef series was equal to that of 

 the control. Series 81 during the 56th-84th generation, was 

 treated with beef for 20 consecutive days. During the first ten 

 days the division rate was slightly less than that of the control. 

 In the second ten period, however the beef series showed a more 

 rapid division rate than the control. Series 95 was treated for 30 

 consecutive days, from the 5Oth-iO2d generation and at no time 

 was there any evidence of stimulation. When the series was 

 again tested in the i6oth, i9Oth and 2ioth generations, the beef 

 series responded with a much higher division rate than the 

 control. Thus all eight series in their later life history responded 

 to beef treatment with an increase in the vitality as indicated by 

 a quickened division rate. The age at which this increase appears 

 varies as would be expected. Series 99, 100, 101, all divided 

 more rapidly in the beef medium at an early age, one as young as 



